This non-provisional application claims priority under 35 U.S.C. § 119(a) on Patent Application No. 2001-304558 filed in Japan on Sep. 28, 2001, which is herein incorporated by reference.
1. Field to the Invention
The present invention relates to a golf club shaft and an iron golf club set and more particularly to a golf club at and an iron golf club set capable of hitting a golf ball a long distance with an improved controlling performance.
2. Description of the Related Art
In recent years, a golf club shaft using a carbon fiber having a high specific strength and specific rigidity is manufactured and commercially available. As the specific strength of the carbon fiber and the specific rigidity thereof have become higher, lightweight golf club shafts can be manufactured.
The use of the carbon fiber having a high specific strength and specific rigidity widens the degree of from in designing the golf club shaft. Thus for example, in recent years, it is possible to design the shaft in such a way as to partially vary the rigidity value thereof. The iron golf club is particularly required to hit a golf ball a long distance with a high degree of control. Thus there have been various attempts made to differentiate the distribution of rigidity in a region of the shaft from that of other regions thereof.
In the iron golf clubs disclosed in Japanese Patent Application Laid-Open No. 2000-126338, the flexural rigidity of a specified position of a higher-numbered golf club (short iron) spaced from the butt thereof is set to be lower than a specified position of a lower-numbered golf club (long iron) spaced from the butt thereof.
However, in the iron golf club set disclosed in Japanese Patent Application Laid Open No. 2000-126338, the rigidity of the shaft at its tip side is not taken into consideration. Thus the golf club does not allow a player to precisely control the flight distance of a golf ball and the like, although it allows the player to hit the golf ball a long distance. The shafts of golf clubs having higher numbers, namely, the short irons, are required to provide an accurate controlling performance. In addition, the shafts are required to have a sufficient flexibility to hit the golf ball high and stop it at a desired position on the green. However, the shaft of the iron golf club disclosed in Japanese Patent Application Laid-Open No. 2000-126338 is incapable of realizing these requirements. Particularly, an iron golf club set is required to provide a reliable performance without being adversely affected by the differences in the lengths of the golf club shafts.
Other proposals have been made to provide a golf club shaft that allows a player to hit a golf ball a long distance and precisely control the flight distance, and the like. As the golf club shaft becomes lightweight, the head speed of the golf club increases and thus a player can hit the golf ball a longer distance compared with conventional clubs. However, the lightweight golf club does not allow incompetent players and aged persons to securely hit the golf ball a sufficiently long distance. Even though a player can hit the golf ball to a target point therewith, the player's performance in controlling the flight distance and the like, deteriorates. Thus the lightweight golf club does not allow a player to precisely control the flight distance and the like, although it allows the player to hit a golf ball a long distance.